Linear to linear motion apparatus including a bidirectional spring clutch having means to inhibit automatic shifting

ABSTRACT

A linear to linear motion apparatus utilizing an output member slidably mounted on a shaft with an input member of circular cross section journalled therein, an elongated rack running through the output member parallel to the shaft and geared to the input member, and a bidirectional spring clutch controlling the relative motion of the input and output members. The clutch comprises a pair of left-hand wound helical springs, oppositely coiled on respective aligned surfaces of the input and output members, controlled by a shifter sleeve, and a third helical spring coiled on the shifter sleeve and an adjoining surface of the output member for inhibiting the automatic shifting of the sleeve. The rack can be run through the output member unidirectionally in either direction, or locked to the output member for advancing it unidirectionally in either direction, as determined by the state of the clutch.

United States Patent [191 Wojtowicz LINEAR TO LINEAR MOTION APPARATUSINCLUDING A BHDHRECTHONAL SPRING CLUTCH HAVING MEANS TO INHIBITAUTOMATIC SHIFTING [75] Inventor: Edward A. Wojtowicz, Bryn Mawr,

Pa. [73] Assignee: Burroughs Corporation, Detroit,

Mich.

[22] Filed: Dec. 27, 1972 [21] Appl. No.: 319,091

[52] US. Cl. 74/89.17, 74/29, 192/41 S [51] Int. Cl. Fl6h 27/02 [58]Field of Search 74/89.17, 29; 192/41 S [5 6] References Cited UNITEDSTATES PATENTS 1,704,062 3/1929 Starkey 192/41 S 2,857,697 10/1958Schutt et al 74/89.l7 2,885,896 5/1959 Hungerford et al. 192/41 S3,429,195 2/1969 Bassoff 74/29 3,475,973 11/1969 Blazek et al. 74/293,668,941 6/1972 Canner 74/89.l7 3,670,861 6/1972 Zenner et a1. 192/41 S1 June 4, 1974 Primary Examiner-Samuel Scott Assistant ExaminerWesley S.Ratliff, Jr.

Fiorito; Paul W. Fish 5 7] ABSTRACT A linear to linear motion apparatusutilizing an output member slidably mounted on a shaft with 'an inputmember of circular cross section journalled therein, an elongated rackrunning through the output member parallel to the shaft and geared tothe input member, and a bidirectional spring clutch controlling therelative motion of the input and output members. The clutch comprises apair of left-hand wound helical springs, oppositely coiled on respectivealigned sur faces of the input and output members, controlled by ashifter sleeve, and a third helical spring coiled on the shifter sleeveand an adjoining surface of the output member for inhibiting theautomatic shifting of the sleeve. The rack can be run through the outputmember unidirectionally in either direction, or locked to the outputmember for advancing it unidirectionally in either direction, asdetermined by the state of the clutch.

10 Claims, 4 Drawing Figures I LINEAR TO LINEAR MOTION APPARATUSINCLUDING A BIDIRECTIONAL SPRING CLUTCH HAVING MEANS TO INHIBITAUTOMATIC SHIP TING BACKGROUND OF THE INVENTION This invention relatesto linear to linear motion devices, and more particularly to suchdevices incorporating a bidirectional spring clutch and including adevice for inhibiting automatic reversal of the clutch.

In the automatic processing of mail a batch of mail is graduallyaccumulated at one position and then advanced to another positionposition for further processing. In one apparatus for handling suchbatches of mail a housing is slidably mounted on a shaft and mailaccumulates between a backing plate and a pivotable forward gate, thepressure of accumulating mail against the forward gate serving toadvance the housing along the shaft. When a batch of mail is accumulatedbetween the backing plate and the gate, the backing plate is advanced,forcing the housing and the batch of mail forward to the next position.Upon arrival at the next processing point, the gate is pivoted upwardlyand the batch of mail discharged. The housing, gate and backing plateare then restored to their original positions.

In the automation of such equipment complex linear relationships arise.During the accumulation of the batch of mail the gate and housing mustmove linearly and freely with respect to the backing plate. After theaccumulation of the batch, the backing plate, forward gate and thehousing must move linearly together. Upon arrival at the next processingstation and the pivoting of the gate, the backing plate must movelinearly with respect to the housing and the forward gate to eject thebatch of mail. All these linear-moves are in the same direction.

After the ejection of the mail the housing, the gate and the backingplate must be moved linearly in the opposite direction and the backingplate may be moved farther linearly, with respect to the housing andgate, to return all the elements of their original positions.

If any controls are mechanically sequenced during the unidirectionalforward motion, the effect of the reversal of the controls during theunidirectional return motion must be timed to permit all elements toreturn to their original positions, including the closing of the gate.

- BRIEF STATEMENT OF THE INVENTION It is, therefore, an object of thisinvention to provide a simple and compact linear to linear motionapparatus for unidirectional movement in either direction, and whereineither of two elements can move freely with respect to the other or belocked together for unitary movement in either direction, according tothe setting of the controls.

It is a further object of the invention to provide means to inhibit theeffect of the automatic reversal of the controls of a linear to linearmotion apparatus until a predetermined state of the apparatus, withina-sequence of events, has been reached.

These objectives are attained by utilizing an output housing slidablymounted on a shaft, an input member of circular cross section journalledin the housing, a pair of similarly wound helical springs oppositelycoiled on respective adjoining surfaces of the output housing and inputmember and a rack running through the housing parallel to the shaft andgeared to the input member. A shifter sleeve for controlling the.engagement of the springs may be biased for normal engagement of one ofthe springs. A third helical spring is coiled on the shifter sleeve andan adjoining surface of the output member for inhibiting the return ofthe shifter sleeve to its normal position under bias. When the shiftersleeve is acting under bias the housing may be advanced unidirectionallyalong the shaft and rack, the input member turning idly in the outputmember, or the rack advanced in the same direction, carrying the housingalong, since the input member cannot reverse direction. Mechanicaldevices may shift the position of the sleeve at any given point ofunidirectional advance, he inhibiting spring acting to retain the sleevein the shifted position against bias. The reverse motion of the rackwill then draw the housing linearly, and the housing can be movedlinearly with respect to the rack in the same direction, until theinhibiting spring is disengaged, and the bias becomes effective toreverse the engagement of the pair of springs.

DESCRIPTION OF THE DRAWINGS For a better understanding of these andother features and advantages of the present invention, reference ismade to the following description and accompanying drawing, in which:

FIG. 1 is an end view of a linear to linear motion apparatusincorporating the concept of the invention;

FIG. 2 is a cross section of the apparatusof the invention taken alongline 2 2 of FIG. 1;

FIG. 3 is a perspective view of the apparatus of FIG. 1, partiallybroken .away, with controls in the same mode as FIG. 1;

FIG. 4 is an'end view of the apparatus of FIG. 1 with the controls inthe reverse mode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT gate 13 leftwardlyalong a shaft 19, as seen in FIG. 1.

The housing 17 is slidably mounted on the shaft 19 and is pierced by anelongated rack 21 to which is affixed the mailbacking plate 15, as byplate 14 and bolts 16. Journalled in the housing 17 is an input drivesleeve 23 of circular cross section (FIG. 2), one end of which is gearedto the rack 21. The shaft 19 and rack 21 are parallel to each other andthe rack 21 runs through the housing 17 perpendicularly to the axis ofrotation of the drive sleeve 23.

A collar 25, integral with and encircling the sleeve 23 intermediate itsends, tits in a channel 27 in the housing 17. The outer surface of thecollar 25 is formed into a pair of shoulders 29, 31 of circular crosssection separated by a ring 33. Aligned with each of the shoulders 29,31 is a surface 35, 37 of circular cross section formed on the housing17.

A left-hand wound helical spring 39 is coiled on the aligned shoulder 29of the collar 25 on the sleeve 23 and surface 35 of the housing 17toward the left from the ring 33, as seen in FIG. 2. Similarly, a secondlefthand wound helical spring 40 is coiled on the aligned shoulder 3i onthe collar 25 of the sleeve 23 and surface 37 of the housing 17 towardthe right as seen in FIG. 2. A tang 41, 43 on the outer end of each ofthe helical drive springs 39, 44 is fixed in housing 17.

A tang 45, 47 on the inner end of each of the helical drive springs 39,40, positioned adjacent the ring 33, has its outer end captured in anindividual short slot 42 (only one shown F l0. 3) in a control sleeve 49journalled on surfaces of the housing 17. The slots 42 are soproportioned and positioned with respect to the tangs 45, 47 on theinner end of the springs 39, 40 that a predetermined, limited clockwiserotation of the sleeve 49 will disengage the spring 39 and leave thespring 40 engaged, and a predetermined limited counterclockwise rotationof the sleeve 49 will disengage the spring 40 and leave the spring 39engaged.

The helical drive springs 39, 40 with the shifter sleeve 49 form aclutch for controlling the relative rotary motion of the sleeve 23 andhousing 17, and thereby the relative linear motion of the housing 17 andthe rack 21 with respect to each other and with respect to the shaft 19.

A spring 51 is connected between the control sleeve 49 and the housing17 for biasing the control sleeve in a clockwise position, as seen inFIG. 1. in the state of the clutch wherein the control sleeve 49 isacting under clockwise bias of spring 51, the left-hand wound drivespring 39 will be disengaged and the left-hand wound drive spring 40engaged. The drive sleeve 23 will, therefore, turn freely, or overrun,counterclockwise against the coils of the engaged spring 40, but cannotturn clockwise because of the locking action of the engaged spring.

Therefore, in the normal condition of the clutch, with the reciprocablecontrol sleeve 49 acting under bias, the housing ll7 may be advancedlinearly along the shaft 19, to the left in HO. 1, or the rack 21retracted linearly through the housing 17, to the right in FIG. l, ineither case turning the drive sleeve 23 idly counterclockwise. However,the housing l7 cannot be retracted along the shaft 19 and rack 21because of the braking effect of the engaged spring 40 on the sleeve 23,and the linear advancement of the rack 21 to the left will also advancethe housing 17 linearly along the shaft 19.

A tab 53 is provided on control sleeve 49 for ease of rotating sleeve 49counterclockwise against the bias of spring 51. When the control sleeve49 is in its counterclockwise position, the drive spring 39 is engagedand the drive spring 40 disengaged. The drive sleeve 23 will, therefore,turn idly clockwise, but be braked against counterclockwise motion.Exactly the opposite linear actions may then be taken as when thecontrol sleeve 49 is in its clockwise position, acting under bias.

Additional configurations of springs for bidirectional spring clutchesare known in the art, such as a pair of right-hand wound helical springswith proper adjustment of the direction of rotation of the controlsleeve and its bias. The choice of spring windings in the clutch of theinvention is a matter of convenience.

The rearward side (right on HO. 2) of the control sleeve 49 rides in anotch 55 in the housing K7 and is aligned with a surface 57 of circularcross section on 4 the housing. A left-hand wound helical spring 59 iscoiled around the rearward side'of the control sleeve 49 and the surface57 of the housing 17 and a tang 61 on the rearward end of the spring 59is embedded in the housing.

A tang 63 on theforward end of the helical spring 59 is fixed in asecond control sleeve 65 journalled on a raised ring 67 on the controlsleeve 49 and a shoulder 69 on the housing 17.

The engagement of helical spring 59 prevents the control sleeve 49 fromshiftingfrom its counterclockwise to its clockwise position under thebias of spring 51. Although the control sleeve 49 may be freely shiftedcounterclockwise against the coils of the helical spring 59, the sleeve49 is inhibited from returning to its clockwise position under the biasof spring 51 by the braking effect of spring 59, when it is engaged.

A tab 72 on the second control sleeve 65 facilitates the shifting ofthat control sleeve counterclockwise to disengage the inhibiting spring59 and to allow the control sleeve 49 to return to its normal clockwiseposition under the bias of spring 51.

The-incorporation of the inhibiting spring 59 with its control sleeve 65in an automatic shifting bidirectional spring clutch provides anadditional element of selective control to permit other desired actionsof the apparatus involved to take place before the automatic shifting ofthe engagement of the pair of springs takes effeet.

It is apparent that the inhibiting spring and its control sleeve of theinvention can be used on an unidirectional spring clutch. Likwise, it isapparent that instead of a single control sleeve for both the drivesprings 39, 40, an individual sleeve for each drive spring withindividual bias can be used and the additional control of an individualinhibiting spring and its control sleeve applied to each drive spring.

In the illustrated apparatus in which the preferred embodiment of theinvention may be utilized, a crank 73 is fixed to a shaft 75 journalledin the sleeve 23 by means of bearings 76. The crank 73 is part of amechanism for pivoting the forward mail gate 13 upwardly and forshifting the control sleeves 49, 65.

The gate 13 is fixed to the shaft 75 by a horizontal bar 80 extendingforwardly from the shaft and, upon the clockwise rotation of the crank73, is pivoted upwardly.

An arm 74 is fixed to the rearward end of the shaft 75 and has anelongated pin 78 mounted on its outward end. The pin 78 extendsforwardly and the arm 74 and pin 78 are so positioned as to interactwith the tab 72 of the control sleeve 65 and to hold the inhibit spring59 out of engagement with the shifter sleeve 49 when mail gate 13 isclosed.

Thus, when gate 13 is closed, the sleeve 65 is held in itscounterclockwise position and the left-hand wound inhibiting spring 59is disengaged and ineffective. However, as the crank 73 begins to turnclockwise to raise the gate 113, the pin 78 is pulled away from the tab72 releasing the inhibiting spring 59 to its normal coiling action whichbrakes any clockwise shift of the sleeve 49. The inhibiting spring 59remains engaged until the gate 13 is returned to its fully closedposition, the arm 74 once more impressing the pin 78 against the tab 72.

The crank 73 has a short arm 81 fixed to the shaft 75 and a longer arm83 substantially orthogonal to the short arm. When the gate 13 isclosed, the arm 81 is substantially horizontal with the arm 83 dependingtherefrom. An elongated slot 85 in the arm 83 has captured therein astud 87 mounted on the longer arm 88 of a bell crank 89 for driving thecrank 73.

The bell crank 89 is pivoted on a shaft 91 journalled in the housing 17and is mechanically oscillated to turn the crank 73 and thereby theshaft 75 by means that will be explained hereinafter.

The longer arm 88 of the bell crank 89 is substantially horizontal whenthe gate 13 is closed and the stud 87 rides in the bottom of the slot85. If the bell crank 89 is rotated counterclockwise about the pivot 91,the stud 87 exerts a force against the inner surface 93 of the slot 85turning the crank 73 clockwise. As the bell crank 89 continues to turncounterclockwise, the stud 87 advances along the surface 93 rotating thecrank 73 substantially 90 and terminating against the inner end of theslot 85, as seen in FIG. 4. in this state of the apparatus the slottedarm 83 of the crank 73 is substantially horizontal and the gate 13 hasbeen rotated upwardly to allow ejection of the mail 11.

In the preferred embodiment of the linear to linear motion apparatus ofthe invention, utilizing the slotted crank 73 and the bell crank 89, anytorque developing on the shaft 75, due to pressure of mail against theclosed forward gate 13, cannot rotate the crank 73 clockwise. Likewise,when the gate 13 is raised, the gravitational force of the weight of thegate cannot rotate the crank 73 counterclockwise. In each case, there isno moment arm to rotate the bell crank 89, as required.

Therefore, due to the preferred arrangement, the gate 13 is in a stableposition both when closed and when open. However, if such stablepositions for gate 13 are not required, the slotted crank 73 and thebell crank 89 can be replaced by meshed counterrotating gears.

A pin 79 is mounted toward the outer end of the longer arm 88 of thebell crank 89 and is positioned to engage the tab 53 of the controlsleeve 49 and shift the sleeve 49 counterclockwise against the bias ofspring 51 as the crank 73 completes its 90 of clockwise rotation underthe impetus of the bell crank 89. The pin 79 maintains the sleeve 49 inits counterclockwise position engaging the drive spring 39 anddisengaging the drive spring 40 as long as the gate I3 is fully open.

When the gate 13 starts to close, the pin 79 starts to withdraw from thetab 53 tending to release it tov the bias of spring 51. However, thehelical spring 59 is now engaged and inhibits the biased clockwise shiftof the control sleeve 49. Only when the gate 13 is completely closed andthe pin 78 shifts the inhibit control sleeve 65 counterclockwise,disengaging the inhibit-spring 59, is the control sleeve 49 allowed toreturn to its clockwise position under the bias of spring 5l.

A notch 95 may be cut out of the arm 88 of the bell crank 89 so as toengage and seat against the shaft 75 as the bell crank completes itscounterclockwise rotation.

A stop 97 (FIG. 4) is positioned in the path of the short arm 99 of thebell crank 89 near the point for opening the gate 13 and ejecting themail 11. As the housing 17 is advanced along the shaft 19, a roller Rmounted near the end of the short arm 99 engages the stop 97 and thecontinued advance of the housing 17 impresses the roller against thestop rotating the bell crank 89 counterclockwise about the pivot 91.

Similarly, a stop 1583 (FIG. l) is positioned to engage the other sideof the roller till, asthe housing is moved rightwardly to its originalposition, for camming the bell crank 89 clockwise back to its originalposition. With the clockwise rotation of the bell crank 89 the stud 87interacts with the slot 85 to rotate the crank 73 back to its originalposition and close the gate 13.

In the operation of the illustrated embodiment of the invention in mailapparatus, mail starts to accumulate between the forward gate 13 and thebacking plate 15 when the housing 1.7 with the gate attached thereto isin a rearward position along the shaft 19 and the rack 2t.

The bell crank 89 has been rotated clockwise, releasing the controlsleeve to the bias of spring 51 and disengaging the inhibit spring 59.The drive spring 39 is disengaged and the drive spring 10 engaged. Thedrive sleeve 23 is, therefore, free to overrun" counterclockwise.

As mail accumulates between the forward gate 13 and the backing plate 15pressure develops against the gate 13 and the housing 17 is allowed tomove linearly along the shaft 19 as the rack 21 turns the drive sleeve23 idly counterclockwise. When a batch" of mail is accumulated betweenthe gate 13 and the backing plate l5, pressure is applied to the rearend of the rack 21 tending to run the rack through the housing 17 andturn the drive sleeve 23 clockwise. The engaged spring 40 brakes suchaction and the housing 17 is moved linearly along with the rack 21advancing the batch of mail along the shaft 19 to the appointed transferposition.

When the roller 101 engages the stop 97 the bell crank 89 is activated,turning the crank 73 clockwise, raising the gate 13, first engaging theinhibiting spring 59 through the release of the inhibiting controlsleeve 65, and later shifting the control sleeve 49 against bias as thegate 13 becomes completely open.

With the reversed application of the drive springs 39, 40, the drivesleeve 23 is free to overrun clockwise, the housing 17 is released fromthe rack 21 for forward motion of the rack, and the rack runs linearlythrough the housing, advancing the backing plate 15 sufficiently toeject the mail 11.

The rack 21 is then retracted linearly tending to turn the drive sleeve23 counterclockwise. The engaged drive spring 39 brakes the drive sleeve23 and the housing 17 is drawn back linearly with the rack 21.

As the rack 21 and housing 17 are retracted, the roller ltll engages thestop 103, rotating the bell crank 89 clockwise and the crank 73counterclockwise immediately removing the pin 79 from the latch 53 ofthe control sleeve 49. However, the engagement of the inhibit spring 59prevents the bias on the control sleeve 49 from switching the engagementof the drive springs 39, 40. The rack 21 and the housing 17 are furtherretracted linearly along the rack 21 to the original position of thehousing.

As the housing 17 is returned to its original position, the rotations ofthe bell crank 89 and crank 73 are completed, shifting the inhibitcontrol sleeve counterclockwise through the interaction of the pin 78 onthe tab 72, releasing the control sleeve 49 to its bias and therebyshifting the engagement of the control spring 39, 40 back to theiroriginal state.

In the preferred embodiment it is only necessary, in the ejection of themail, to advance the backing plate E5 to substantially its originalposition relative to the the housing 17 as the shaft 75 is rotated,opening the gate 13. However, this change in the relative positions ofthe housing 17 and backing plate l will be exactly compensated for asthe gate 13 is being closed in the retraction of the housing.

In the preferred embodiment, therefore, the housing 17 and rack 21 maybe retracted together and, upon the closing of gate 13, the variouselements of the apparatus will be in their original positions.

If it is necessary, however, to run the rack 21 and backing plate 115somewhat farther forward, in the ejection of the mail, than theiroriginal position relative to the housing 17, the rack 21. can beretracted farther to its original position, after the gate 13 is closedand the inhibit spring 59 released, idly turning the drive sleeve 23counterclockwise.

The clutch of the invention, although simple in construction andoperation, permits a housing to move unidirectionally in eitherdirection, with respect to a drive rack, or the drive rack to moveunidirectionally, in either direction, through the housing, or thehousing to be locked to the drive rack for movement unidirectionally, ineither direction with the rack, with a minimum of controls, the inhibitspring and its control giving maximum flexibility as to staying theeffect of automatic shifting of the drive springs.

Additionally, the inhibit spring and its control sleeve can perform amemory function in the clutch in that the state of the clutch ismaintained, despite the functioning of automatic shift apparatus, untilit is desired to release the clutch to the automatic function.

What is claimed is:

l. A linear to linear motion apparatus comprising:

a housing mounted for free linear movement in either direction;

a drive member rotatably journalled in said housing, the axis ofrotation being orthogonal to said linear movement;

an elongated toothed member slidably mounted in said housing andorthogonally geared to said drive member; and

means for controlling the rotation in either direction and non-rotationof said drive member with respect to said housing.

2. The linear to linear motion apparatus of claim 1 wherein saidcontrolling means is a bidirectional clutch.

3. The linear to linear motion apparatus of claim 2 wherein saidbidirectional clutch includes a pair of helical springs coiled onrespective adjoining surfaces of said drive member and said housing.

s. The linear to linear motion apparatus of claim 1 wherein said drivemember and said housing have a plurality of abutting surfaces ofcircular cross section and wherein said controlling means includes apair of helical springs coiled on respective ones of said abuttingsurfaces in opposed relationship.

5. The linear to linear motion apparatus of claim 4' wherein saidcontrolling means also includes reciprocable means slidably mounted onsaid housing and wherein said pair of springs are like wound andoppositely coiled on said respective abutting surfaces with one end ofeach of said springs being captured in said reciprocable means forengaging one spring and disengaging the other spring by the shifting ofsaid reciprocable means.

6. The linear to linear motion apparatus of claim 5 wherein saidreciprocable means is a control sleeve journalled on the surfaces ofsaid housing, said sleeve having short slots therein for receiving saidcaptured ends and wherein the other ends of said springs are imbedded insaid housing.

7. The linear to linear motion apparatus of claim 6 wherein said controlsleeve is biased for engagement of one of said springs and disengagementof the other and wherein said controlling means also includes means forshifting said control sleeve against bias.

8. The linear to linear motion apparatus of claim 7 wherein said controlsleeve and said housing also having abutting surfaces of circular crosssection and wherein said controlling means also includes a third helicalspring coiled on said abutting surfaces of said sleeve and said housingfor inhibiting the return of said control sleeve under bias from itsshifted position when said third helical spring is engaged.

9. The linear to linear apparatus of claim 8 wherein said controllingmeans also includes means for normally holding said third springdisengaged and said controlling of means further includes means forreleas-.

ing said holding means.

10. The linear to linear apparatus of claim 9 also including means forlimiting the excursion of said housing in each direction and whereinsaid controlling means also includes means interacting with saidlimiting means at one end of said excursion for automatically firstactuating said releasing means and then activating said shifting meansand for interacting with said limiting means at the other end of saidexcursion for first deactivating said shifting means and thenreactivating said holding means.

1. A linear to linear motion apparatus comprising: a housing mounted forfree linear movement in either direction; a drive member rotatablyjournalled in said housing, the axis of rotation being orthogonal tosaid linear movement; an elongated toothed member slidably mounted insaid housing and orthogonally geared to said drive member; and means forcontrolling the rotation in either direction and nonrotation of saiddrive member with respect to said housing.
 2. The linear to linearmotion apparatus of claim 1 wherein said controlling means is abidirectional clutch.
 3. The linear to linear motion apparatus of claim2 wherein said bidirectional clutch includes a pair of helical springscoiled on respective adjoining surfaces of said drive member and saidhousing.
 4. The linear to linear motion apparatus of claim 1 whereinsaid drive member and said housing have a plurality of abutting surfacesof circular cross section and wherein said controlling means includes apair of helical springs coiled on respective ones of said abuttingsurfaces in opposed relationship.
 5. The linear to linear motionapparatus of claim 4 wherein said controlling means also includesreciprocable means slidably mounted on said housing and wherein saidpair of springs are like wound and oppositely coiled on said respectiveabutting surfaces with one end of each of said springs being captured insaid reciprocable means for engaging one spring and disengaging theother spring by the shifting of said reciprocable means.
 6. The linearto linear motion apparatus of claim 5 wherein said reciprocable means isa control sleeve journalled on the surfaces of said housing, said sleevehaving short slots therein for receiving said captured ends and whereinthe other ends of said springs are imbedded in said housing.
 7. Thelinear to linear motion apparatus of claim 6 wherein said control sleeveis biased for engagement of one of said springs and disengagement of theother and wherein said controlling means also includes means forshifting said control sleeve against bias.
 8. The linear to linearmotion apparatus of claim 7 wherein said control sleeve and said housingalso having abutting surfaces of circular cross section and wherein saidcontrolling means also includes a third helical spring coiled on saidabutting surfaces of said sleeve and said housing for inhibiting thereturn of said control sleeve under bias from its shifted position whensaid third helical spring is engaged.
 9. The linear to linear apparatusof claim 8 wherein said controlling means also includes means fornormally holding said third spring disengaged and said controlling ofmeans further includes means for releasing said holding means.
 10. Thelinear to linear apparatus of claim 9 also including means for limitingthe excursion of said housing in each direction and wherein saidcontrolling means also includes means interacting with said limitingmeans at one end of said excursion for automatically first actuatingsaid releasing means and then activating said shifting means and forinteracting with said limiting means at the other end of said excursionfor first deactivating said shifting means and then reactivating saidholding means.